陈皮对土壤中六价铬的去除效果及机理
Effect of tangerine peel on the removal efficiency of Cr(VI) in soil and its underlying mechanism
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摘要: 获取廉价、易得且环境友好的高效修复药剂是Cr(Ⅵ)污染土壤修复的重要工作之一. 基于室内模拟培养试验,研究了陈皮添加量和土壤中Cr(Ⅵ)初始浓度对Cr(Ⅵ)去除过程的影响,通过Illumina NovaSeq高通量测序技术和X射线近边吸收光谱(XANES)等方法初步探讨了陈皮修复Cr(Ⅵ)污染土壤的机理. 当土壤中Cr(Ⅵ)初始浓度为(1600.13±298.11) mg/kg、Cr(Ⅵ)浸出浓度为(143.20±13.5) mg/L,陈皮添加量为5%时培养30 d后,土壤中Cr(Ⅵ)浓度及其浸出浓度分别降至(10.07±2.98) mg/kg和(1.02±0.30) mg/L,去除率分别达到99.37%和99.29%. 结果表明,土壤中Cr(Ⅵ)的去除效率随陈皮添加量的增加而增大,随Cr(Ⅵ)初始浓度的增加而减小,且添加陈皮后土壤中的Cr(Ⅵ)转化为生物有效性较低的Cr(Ⅲ). 此外,陈皮影响了Cr(Ⅵ)污染土壤中细菌群落结构及其组成. 添加陈皮降低土壤中细菌群落的α多样性,并改变了细菌群落的β多样性. 在添加陈皮后的土壤中,放线菌门(Actinobacteria)为最优菌门,微杆菌属(Microbacterium)、土壤球菌属(Agrococcus)、链球菌属(Streptococcus)和链霉菌属(Streptomyces)4种Cr(Ⅵ)还原菌富集.[A1] [A2] 研究显示,陈皮能在较短时间内有效降低污染土壤中Cr(Ⅵ)浓度及其浸出浓度. 它的去除机制可能是:①通过在土壤中水解的小分子有机物直接将Cr(Ⅵ)还原为Cr(Ⅲ);②作为碳源,驱动Cr(Ⅵ)还原菌的富集进而间接降低Cr(Ⅵ)的毒性.Abstract: The search for inexpensive, high volume, easily accessible and environmentally friendly efficient remediation agents is one of the important tasks in the remediation of Cr(VI)-contaminated soil at this stage. Based on indoor simulated incubation experiments, the effects of tangerine peel addition and the initial concentration of Cr(VI) in soil on the removal process of Cr(VI) were studied, and the mechanism of tangerine peel remediation of Cr(VI)-contaminated soil was initially explored by Illumina NovaSeq high-throughput sequencing technology and X-ray near edge absorption spectroscopy (XANES). When the initial concentration of Cr(VI) in soil was (1600.13±298.11) mg/kg, the Cr(VI)-leaching concentration of Cr(VI) was (143.20±13.5) mg/L, and the amount of tangerine peel was added at 5% for 30 d, the concentration of Cr(VI) and its leaching concentration in soil decreased to (10.07±2.98) mg/kg and (1.02±0.30) mg/L, and the removal rates reached 99.37% and 99.29%, respectively. The results showed that the removal efficiency of Cr(VI) in soil increased with the increase of tangerine peel addition and decreased with the increase of the initial concentration of Cr(VI), the Cr(VI) in soil was converted to the Cr(III) after the addition of tangerine peel. In addition, tangerine peel affected the structure of bacterial community and its composition in Cr(VI)-contaminated soils. Addition of tangerine peel reduced the α-diversity and changed the β-diversity of bacterial communities. In the soil after the addition of tangerine peel, Actinobacteria was the optimal phylum, and four Cr(VI)-reducing bacteria, Microbacterium, Agrococcus, Streptococcus and Streptomyces, were enriched. The study showed that tangerine peel could effectively reduce the concentration of Cr(VI) and its leaching concentration in contaminated soil in a relatively short period of time. Its removal mechanism may be: (i) direct reduction of Cr(VI) to Cr(III) through small molecule organic matter hydrolyzed in the soil; (ii) indirect reduction of Cr(VI) toxicity by driving the enrichment of Cr(VI)-reducing bacteria as a carbon source.
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